Websites do not loaded properly in Nginx loadbalancing

I have 3 Nginx Servers like this -

• lab01.net => 192.168.89.128 (load balancer)
• lab02.net => 192.168.89.129 (backend)
• lab03.net => 192.168.89.130 (backend)

-------------- lab01.net configuration ----------

upstream backend {
        server  lab02.net:443;
        server  lab03.net:443;
}



server {
        listen  80;
        listen  [::]:80;

        server_name     lab01.net;
        return  301     https://lab01.net$request_uri;
}

server {
        listen  443 ssl http2;
        listen  [::]:443 ssl http2;
        server_name     lab01.net;

        ssl_certificate /etc/nginx/ssl/ssl.pem;
        ssl_certificate_key     /etc/nginx/ssl/ssl.key;

        location / {
                proxy_pass      https://backend;
                proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header        X-Real-IP $remote_addr;
                proxy_set_header        Host $host;
        }

}

------------------- lab02.net configuration --------------------------

server {
        listen  8080;
        listen  [::]:8080;

        server_name     lab02.net;
        return  301     https://lab02.net$request_uri;
}

server {
        listen  443 ssl http2;
        listen  [::]:443 ssl http2;
        server_name     lab02.net;

        root    /srv/www/en;
        index   index.html index.htm;

        ssl_certificate /etc/nginx/ssl/ssl.pem;
        ssl_certificate_key     /etc/nginx/ssl/ssl.key;

}

------------------- lab03.net configuration -----------------------

server {
        listen  8080;
        listen  [::]:8080;

        server_name     lab03.net;
        return  301     https://lab03.net$request_uri;
}

server {
        listen  443 ssl http2;
        listen  [::]:443 ssl http2;
        server_name     lab03.net;

        root    /srv/www/es;
        index   index.html index.htm;

        ssl_certificate /etc/nginx/ssl/ssl.pem;
        ssl_certificate_key     /etc/nginx/ssl/ssl.key;

}

Firewalld 8080, HTTP, and HTTPS are allowed on all servers.

Selinux Policy "semanage fcontext -a -t httpd_sys_content_t "/srv/www(/.*)?" is on each lab02.net and lab03.net servers and "setsebool -P httpd_can_network_connect" on lab01.net Nginx load balancer.

All works fine and the problem is that when I load the websites they do not appear correctly. The letters, images, content, etc... are not in a place where they belong to. When I use just only index.html to test it's just fine but when I use real HTML and CSS template website, the problem starts to appear.